Portable power tools having rotational output are widely used. Many portable power tools do not have brake function. Generally, after the operation of a portable power tool, an operator has to hold the power tool for a period of time until the spindle of the power tool is totally stopped. Then, the operator can put the tool down. This is time-consuming and not convenient for the operator. In addition, it has a high risk of injury. Specifically, if the operator puts down the tool when the spindle of the tool is still rotating, the tool may hurt other items or people.
For addressing this problem, some portable power tools are equipped with a brake for stopping the tool quickly and smoothly, which gives the operator higher safety and better feeling.
In the prior art, one solution for stopping the tool is using an electrically controlled brake for providing a braking force to the power tool. The tool comprises a braking module, located between a motor and a power supply, for applying a current limited braking force to the motor when the power supply is disconnected from the motor. The electrically controlled brake has high cost and low reliability.
Another solution is using a mechanical brake, like the brakes adopted in vehicles. Specifically, a brake wheel is fixed on a motor spindle of the power tool, and a lever covered with rubber is adapted to contact and stop the brake wheel under the force of a compression spring. The manipulation of the mechanical brake is independent of the operation of the motor. That is to say, after the operation of the tool, the operator needs to perform an additional action to stop the tool. This is cumbersome.
Further, sometimes it needs that, after the operation of the tool, the spindle of the tool is locked from rotation for the purpose of, for example, exchanging the tool head or tool bit which is driven by the spindle. Although conventional power tools with brake can stop quickly after operation, their spindles are not locked in place from rotation.
Thus, it is desirable to provide a portable power tool with a simple and reliable brake, which can stop the spindle of the tool quickly and smoothly after operation and lock the spindle to prevent it from rotation.